1. Field of the Invention
This invention generally relates to data processing systems and most particularly a microprocessor based data processor having a programmable graphics generator.
2. Background Discussion
Recent years have seen spectactular breakthroughs in the electronics industry in the area of microelectronics. Witness the variety and computing capabilities of the plethora of handheld calculators on the market today. These breakthroughs have made available for public consumption microprocessor units, essentially computers in very small packages, which have found their way in to a variety of consumer products--from microwave oven control to electronic games.
Now, a new industry is in the throes of formation. Based upon creative use of commercially available microprocessor units--such as the microcomputer manufactured by MOS Technology Inc., part number MCS6500--the public is being introduced to small, efficient data processing systems for home or (small) business use. These microprocessor data processing systems are available for a variety of personal uses, depending upon the particular software (programming) that accompanies the unit, ranging from programmed instruction, checklist balancing, mailing list sorts and updates, to entertainment games.
Information provided by a data processor system is commonly presented to a viewer via some type of printer unit or a video display unit. The printer has the advantage of providing the information in a relatively permanent form. The display unit displays information only while the unit is on, but a significant advantage of video display units is that much of the public possesses one in the form of a television receiver. Thus, there is already readily available to many potential purchasers of microprocessor based data processing systems a device, the television receiver, that can easily provide machine to man communication. Accordingly, many if not all microcomputer data processing systems are structured to communicate with raster-scan type video units (i.e., television receivers).
Presently available microcomputer units are usually characterized as very simple in detail but extremely complex in their overall operation. Relatively complex tasks are carried out by these microcomputers by performing a large number of simple operations. Thus, when processing such data--be it for an entertainment game or computing numeric amounts--the microcomputer actually may perform an extremely large number of these simple operations. In addition to its data processing functions, the microcomputer must effectively control the information transmission to the video display unit, including what and how the information is displayed. The microcomputer must, therefore, share its operation time between these two functions: data processing and information display control; and as one function places greater time-consuming demands upon the microcomputer unit, the other suffers accordingly.
As a result, many personal microprocessor based data processing systems tend to be somewhat slow in communicating the results of complex tasks to the user. Some attempts have been made to alleviate this annoying problem, however, but the result has not been altogether too satisfying. For example, one solution is to keep the tasks to be performed by the microcomputer relatively less complex. The number of individual operations required to perform the simpler tasks would be less and would, therefore, take less time. This solution, unfortunately, can severely limit the processing capability of the microprocessor and the system. Another solution to the time problem is to increase the throughput of the microprocessor; that is to increase the size (e.g. number of bits) of the data word the microprocessor is capable of operating on. For example, if the microprocessor is designed to handle 8-bit data words (as most presently available microprocessors are), build a microprocessor capable of handling 12 or 16-bit words. However, as the word size handled by the microprocessor increases, so does the complexity, size and expense of the microprocessor--usually at a geometric rate. The present advantages of presently available large-scale, single-chip programmable microprocessors--that of being powerful, inexpensive, easy-to-use device--may be lost.